Running economy (RE) a complex, multifactorial concept that represents the sum of metabolic, cardiorespiratory, biomechanical and neuromuscular efficiency during running. Oxygen consumption (VO2) is the most commonly used method for measuring running economy, as the exchange of gases in the body, specifically oxygen and carbon dioxide, closely reflects energy metabolism. Those who are able to consume less oxygen while running at a given velocity are said to have a better running economy. However, straightforward oxygen usage does not account for whether the body is metabolising lipids or carbohydrates, which produce different amounts of energy per unit of oxygen; as such, accurate measurements of running economy must use and data to estimate the calorific content of the substrate that the oxygen is being used to respire.
In distance running, an athlete may attempt to improve performance through training designed to improve running economy. Running economy has been found to be a good predictor of race performance; it has been found to be a stronger correlate of performance than maximal oxygen uptake (VO2 max) in trained runners with the same values.
The idea of running economy is increasingly used to understand performance, as new technology can drastically lower running times over marathon distances, independently of physiology or even training. Factors affecting running economy include a runner’s biology, training regimens, equipment, and environment. The recent accomplishment of Eliud Kipchoge running a marathon in under two hours has enhanced interest in the subject.
Measurement and values
Measurement
Running Economy is calculated by measuring VO₂ while running on a treadmill at various constant speeds for anywhere between three and fifteen minutes. VO₂ is the amount of oxygen consumed in milliliters over one minute and normalized by kilogram of body weight. To compare running economies between individuals, VO₂ is interpolated to common running velocities while also quantifying how much oxygen is needed to run one kilometer relative to body mass. A lower value of running economy demonstrates better running efficiency and provides a good predictor for race performance. A new method for measuring such concepts can be found with the help of the use of wireless foot-worn inertial sensors together with dedicated signal processing algorithms.
Values of running economy
Factors affecting running economy
In The Lore of Running, Tim Noakes, a professor of exercise and sports science at the University of Cape Town, and also recreational runner, describes a number of variables that may affect running economy: vertical motion while running, the ability of the muscles to absorb energy during the shock of landing and transfer it to push-off, biomechanical factors, technique and type of activity, fitness and training, age, fatigue, gender, race, weight of clothing and shoes, and environmental conditions.
Various studies have shown marathon runners to be more economical than middle distance runners and sprinters at speeds of 6–12 miles per hour (10-19 kilometers per hour). At those speeds, film analysis has shown that sprinters and middle distance have more vertical motion than marathoners.
Anthropometry
Running economy also depends on many innate characteristics with some body characteristics naturally giving runners an advantage. Some of these include height, limb length, and body mass distribution in certain areas of the body.
Limbs are a greater distance from a person’s center of mass, so they have greater rotational inertia compared to the rest of the body. As a result, limbs require more energy to move, so their morphology plays a role in running economy. In the legs, an increased weight in the feet relates to running economy since they are located most distally from the hips, slightly smaller than average feet are ideal for optimizing running economy. This is also why shoe choice affects running economy. Weight carried in the thighs also plays a role with weight distributed closer to the hip joint, but does affect running economy as much as foot morphology. In one study, weights were added to the runners’ feet and thighs and they found that VO₂ consumption increased twice as much in trials with weights on feet compared to thighs. While the distribution of mass in limbs has been correlated to running economy, there is no consensus on whether or not limb length is a factor.